// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
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//    notice, this list of conditions and the following disclaimer.
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//    notice, this list of conditions and the following disclaimer in the
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//
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package org.objectweb.asm;

/**
 * A visitor to visit a Java class. The methods of this class must be called in the following order: {@code visit} [ {@code visitSource} ] [ {@code visitModule} ][ {@code visitNestHost} ][ {@code
 * visitOuterClass} ] ( {@code visitAnnotation} | {@code visitTypeAnnotation} | {@code
 * visitAttribute} )* ( {@code visitNestMember} | {@code visitInnerClass} | {@code visitField} | {@code visitMethod} )* {@code visitEnd}.
 *
 * @author Eric Bruneton
 */
public abstract class ClassVisitor {

	/**
	 * The ASM API version implemented by this visitor. The value of this field must be one of {@link Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
	 */
	protected final int api;

	/** The class visitor to which this visitor must delegate method calls. May be null. */
	protected ClassVisitor cv;

	/**
	 * Constructs a new {@link ClassVisitor}.
	 *
	 * @param api
	 *          the ASM API version implemented by this visitor. Must be one of {@link Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
	 */
	public ClassVisitor(final int api) {
		this(api, null);
	}

	/**
	 * Constructs a new {@link ClassVisitor}.
	 *
	 * @param api
	 *          the ASM API version implemented by this visitor. Must be one of {@link Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
	 * @param classVisitor
	 *          the class visitor to which this visitor must delegate method calls. May be null.
	 */
	public ClassVisitor(final int api, final ClassVisitor classVisitor) {
		if (api != Opcodes.ASM7 && api != Opcodes.ASM6 && api != Opcodes.ASM5 && api != Opcodes.ASM4) {
			throw new IllegalArgumentException("Unsupported api " + api);
		}
		this.api = api;
		this.cv = classVisitor;
	}

	/**
	 * Visits the header of the class.
	 *
	 * @param version
	 *          the class version. The minor version is stored in the 16 most significant bits, and the major version in the 16 least significant bits.
	 * @param access
	 *          the class's access flags (see {@link Opcodes}). This parameter also indicates if the class is deprecated.
	 * @param name
	 *          the internal name of the class (see {@link Type#getInternalName()}).
	 * @param signature
	 *          the signature of this class. May be {@literal null} if the class is not a generic one, and does not extend or implement generic classes or interfaces.
	 * @param superName
	 *          the internal of name of the super class (see {@link Type#getInternalName()}). For interfaces, the super class is {@link Object}. May be {@literal null}, but only for the {@link Object} class.
	 * @param interfaces
	 *          the internal names of the class's interfaces (see {@link Type#getInternalName()}). May be {@literal null}.
	 */
	public void visit(final int version, final int access, final String name, final String signature,
			final String superName, final String[] interfaces) {
		if (cv != null) {
			cv.visit(version, access, name, signature, superName, interfaces);
		}
	}

	/**
	 * Visits the source of the class.
	 *
	 * @param source
	 *          the name of the source file from which the class was compiled. May be {@literal
	 *     null}.
	 * @param debug
	 *          additional debug information to compute the correspondence between source and compiled elements of the class. May be {@literal null}.
	 */
	public void visitSource(final String source, final String debug) {
		if (cv != null) {
			cv.visitSource(source, debug);
		}
	}

	/**
	 * Visit the module corresponding to the class.
	 *
	 * @param name
	 *          the fully qualified name (using dots) of the module.
	 * @param access
	 *          the module access flags, among {@code ACC_OPEN}, {@code ACC_SYNTHETIC} and {@code
	 *     ACC_MANDATED}.
	 * @param version
	 *          the module version, or {@literal null}.
	 * @return a visitor to visit the module values, or {@literal null} if this visitor is not interested in visiting this module.
	 */
	public ModuleVisitor visitModule(final String name, final int access, final String version) {
		if (api < Opcodes.ASM6) {
			throw new UnsupportedOperationException("This feature requires ASM6");
		}
		if (cv != null) {
			return cv.visitModule(name, access, version);
		}
		return null;
	}

	/**
	 * Visits the nest host class of the class. A nest is a set of classes of the same package that share access to their private members. One of these classes, called the host, lists the other members of the nest, which in turn should link to the host of their nest. This method must be called only once and only if the visited class is a non-host member of a nest. A class is implicitly its own nest, so it's invalid to call this method with the visited class name as argument.
	 *
	 * @param nestHost
	 *          the internal name of the host class of the nest.
	 */
	public void visitNestHost(final String nestHost) {
		if (api < Opcodes.ASM7) {
			throw new UnsupportedOperationException("This feature requires ASM7");
		}
		if (cv != null) {
			cv.visitNestHost(nestHost);
		}
	}

	/**
	 * Visits the enclosing class of the class. This method must be called only if the class has an enclosing class.
	 *
	 * @param owner
	 *          internal name of the enclosing class of the class.
	 * @param name
	 *          the name of the method that contains the class, or {@literal null} if the class is not enclosed in a method of its enclosing class.
	 * @param descriptor
	 *          the descriptor of the method that contains the class, or {@literal null} if the class is not enclosed in a method of its enclosing class.
	 */
	public void visitOuterClass(final String owner, final String name, final String descriptor) {
		if (cv != null) {
			cv.visitOuterClass(owner, name, descriptor);
		}
	}

	/**
	 * Visits an annotation of the class.
	 *
	 * @param descriptor
	 *          the class descriptor of the annotation class.
	 * @param visible
	 *          {@literal true} if the annotation is visible at runtime.
	 * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not interested in visiting this annotation.
	 */
	public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) {
		if (cv != null) {
			return cv.visitAnnotation(descriptor, visible);
		}
		return null;
	}

	/**
	 * Visits an annotation on a type in the class signature.
	 *
	 * @param typeRef
	 *          a reference to the annotated type. The sort of this type reference must be {@link TypeReference#CLASS_TYPE_PARAMETER}, {@link TypeReference#CLASS_TYPE_PARAMETER_BOUND} or {@link TypeReference#CLASS_EXTENDS}. See {@link TypeReference}.
	 * @param typePath
	 *          the path to the annotated type argument, wildcard bound, array element type, or static inner type within 'typeRef'. May be {@literal null} if the annotation targets 'typeRef' as a whole.
	 * @param descriptor
	 *          the class descriptor of the annotation class.
	 * @param visible
	 *          {@literal true} if the annotation is visible at runtime.
	 * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not interested in visiting this annotation.
	 */
	public AnnotationVisitor visitTypeAnnotation(final int typeRef, final TypePath typePath, final String descriptor,
			final boolean visible) {
		if (api < Opcodes.ASM5) {
			throw new UnsupportedOperationException("This feature requires ASM5");
		}
		if (cv != null) {
			return cv.visitTypeAnnotation(typeRef, typePath, descriptor, visible);
		}
		return null;
	}

	/**
	 * Visits a non standard attribute of the class.
	 *
	 * @param attribute
	 *          an attribute.
	 */
	public void visitAttribute(final Attribute attribute) {
		if (cv != null) {
			cv.visitAttribute(attribute);
		}
	}

	/**
	 * Visits a member of the nest. A nest is a set of classes of the same package that share access to their private members. One of these classes, called the host, lists the other members of the nest, which in turn should link to the host of their nest. This method must be called only if the visited class is the host of a nest. A nest host is implicitly a member of its own nest, so it's invalid to call this method with the visited class name as argument.
	 *
	 * @param nestMember
	 *          the internal name of a nest member.
	 */
	public void visitNestMember(final String nestMember) {
		if (api < Opcodes.ASM7) {
			throw new UnsupportedOperationException("This feature requires ASM7");
		}
		if (cv != null) {
			cv.visitNestMember(nestMember);
		}
	}

	/**
	 * Visits information about an inner class. This inner class is not necessarily a member of the class being visited.
	 *
	 * @param name
	 *          the internal name of an inner class (see {@link Type#getInternalName()}).
	 * @param outerName
	 *          the internal name of the class to which the inner class belongs (see {@link Type#getInternalName()}). May be {@literal null} for not member classes.
	 * @param innerName
	 *          the (simple) name of the inner class inside its enclosing class. May be {@literal null} for anonymous inner classes.
	 * @param access
	 *          the access flags of the inner class as originally declared in the enclosing class.
	 */
	public void visitInnerClass(final String name, final String outerName, final String innerName, final int access) {
		if (cv != null) {
			cv.visitInnerClass(name, outerName, innerName, access);
		}
	}

	/**
	 * Visits a field of the class.
	 *
	 * @param access
	 *          the field's access flags (see {@link Opcodes}). This parameter also indicates if the field is synthetic and/or deprecated.
	 * @param name
	 *          the field's name.
	 * @param descriptor
	 *          the field's descriptor (see {@link Type}).
	 * @param signature
	 *          the field's signature. May be {@literal null} if the field's type does not use generic types.
	 * @param value
	 *          the field's initial value. This parameter, which may be {@literal null} if the field does not have an initial value, must be an {@link Integer}, a {@link Float}, a {@link Long}, a {@link Double} or a {@link String} (for {@code int}, {@code float}, {@code long} or {@code String} fields respectively). <i>This parameter is only used for static fields</i>. Its value is ignored for non static fields, which must be initialized through bytecode instructions in constructors or methods.
	 * @return a visitor to visit field annotations and attributes, or {@literal null} if this class visitor is not interested in visiting these annotations and attributes.
	 */
	public FieldVisitor visitField(final int access, final String name, final String descriptor, final String signature,
			final Object value) {
		if (cv != null) {
			return cv.visitField(access, name, descriptor, signature, value);
		}
		return null;
	}

	/**
	 * Visits a method of the class. This method <i>must</i> return a new {@link MethodVisitor} instance (or {@literal null}) each time it is called, i.e., it should not return a previously returned visitor.
	 *
	 * @param access
	 *          the method's access flags (see {@link Opcodes}). This parameter also indicates if the method is synthetic and/or deprecated.
	 * @param name
	 *          the method's name.
	 * @param descriptor
	 *          the method's descriptor (see {@link Type}).
	 * @param signature
	 *          the method's signature. May be {@literal null} if the method parameters, return type and exceptions do not use generic types.
	 * @param exceptions
	 *          the internal names of the method's exception classes (see {@link Type#getInternalName()}). May be {@literal null}.
	 * @return an object to visit the byte code of the method, or {@literal null} if this class visitor is not interested in visiting the code of this method.
	 */
	public MethodVisitor visitMethod(final int access, final String name, final String descriptor, final String signature,
			final String[] exceptions) {
		if (cv != null) {
			return cv.visitMethod(access, name, descriptor, signature, exceptions);
		}
		return null;
	}

	/**
	 * Visits the end of the class. This method, which is the last one to be called, is used to inform the visitor that all the fields and methods of the class have been visited.
	 */
	public void visitEnd() {
		if (cv != null) {
			cv.visitEnd();
		}
	}
}
